The principal theme among the clinical projects in this Specialized Center of Research in Thrombosis is the unravelling of the process of intravascular coagulation sufficiently to recognize thrombosis in its incipient and overt stages. Related to the clinical studies are several projects concerned with the mechanism of thrombus formation. In this regard individual and interdisciplinary investigations are ongoing in the areas of surface, biologically active substances such as platelet membranes, activated species of clotting factors, and thrombus detection by isotopic techniques.